PHP 關於foreach 中修改array中元素的值

PHP中支持使用引用'&'，用法與C基本一樣，個人理解就是函數中引用的變量指針直接指向了傳入參數的源地址，所以使用引用還是存在一定的危險性。所以對於一重循環，建議不使用引用，直接修改原array即可

        $table_exchange=array();
        array_push($table_exchange, array(
        "cnid" => '123',
        "status" =>  0,
        "checked" => false,
        "leaf" => true
        ));
        foreach ($table_exchange as $b=> $c) 
        {

            $table_exchange[$b]['cnid']= '222';
        }
        echo json_encode($table_exchange);

輸出：

[{"cnid":"222","status":0,"checked":false,"leaf":true}]

而在操作復雜的多重循環中，使用引用會方便許多，也更加便於理解和操作，例如：

         $nodeList=array();
        array_push($nodeList, array(
        "cnid" => '1',
        "status" =>  1,
        "checked" => false,
        "leaf" => true
        ));

        $table_exchange=array();
        array_push($table_exchange, array(
        "cnid" => '2',
        "status" =>  0,
        "checked" => false,
        "children" => $nodeList,
        "leaf" => false
        ));

        
        foreach ($table_exchange as $b=>& $c){
            
            foreach($c['children'] as $b2=>& $d){
                $d['cnid']='000';
            }
        }
        
        echo json_encode($table_exchange);//轉成json格式輸出到網頁顯示結果

輸出：[{"cnid":"2","status":0,"checked":false,"children":[{"cnid":"000","status":1,"checked":false,"leaf":true}],"leaf":true}]